I am not sure this forum is the right place for this question, but I'm pretty sure it would quickly be closed at MathOverflow.
There is a well-known mathematics journal called "International Mathematics Research Notices", published by OUP. It's almost invariably cited as "Int. Math. Res. Not. IMRN" [sic] or similar, which has always struck me as oddly redundant. The curious ubiquity of the abbreviation is doubtless due to the fact that MathSciNet provides references in that format: "JOURNAL = {Int. Math. Res. Not. IMRN}".
On the other hand, Worldcat has many listings for the journal, some of which have the double IMRN, and some of which don't. As far as I can tell, the journal's page doesn't specify a preferred abbreviated form.
Another possibly relevant factor is that the journal is usually referred to be this initialism: people call it "IMRN" in ordinary conversation, which isn't the case for any other journals I can think of, JAMS perhaps excepted if you count pronouncing it (and nobody writes "J. Am. Math. Soc. JAMS").
The question: why does MathSciNet double the journal name, and should I be doing the same? (Perhaps the underlying question is: who decides on official journal abbreviations?)